1. Warm Up “What factors might change a population size?”
“What kind of relationships do organisms have?”
“What factors might change a population size?”

2. Question: What does it mean when a population increases or decreases in size with respect to birth rates and death rates?

3. Chapter 5 Populations

4. Ch. 5 Objectives – Sections 1 and 2
List the characteristics used to describe a population.
Identify factors that affect population size.
Differentiate between exponential and logistic growth.
Identify factors that limit population growth.
Differentiate between density-dependent and density-independent limiting factors.

5. Section 5.1
How Populations Grow

6. What is a population?
A group of organisms of the same species living in the same area

7. Characteristics of a Population
4 ways to describe a population:
Geographic distribution: where the pop. lives
Population density: # of individuals / unit area
Ex. 150 frogs live in a pond that is 3 square kilometers. What is the population density?
Population growth rate
Age structure

8. Population Growth
Is a measured a rate of how fast (or slow) a population is growing. It is the size of a population over time.
A negative value for population growth rate means the population is decreasing.

9. Population Growth 3 factors that affect pop. size: # births # deaths
# individuals that enter or leave
Growth = (Births + immigrants) – (Death + emmigrants)

10. Population Growth Immigration: individuals move into an area
Emigration: individuals move out of an area

11. Exponential Growth “J-curve”
Occurs when indiv. in population reproduce at constant rate
Needs ideal conditions and unlimited resources
From graphs – what would happen if populations grew uncontrollably??

12. Logistic growth “S-curve”
Population’s growth slows/stops following exponential growth
Occurs when resources are less available
Population reaches carrying capacity: largest # of indiv. an environment can support

13. Section 5.2
Limits to Growth

14. Limiting Factors
Causes pop. growth to decrease

15. Density-Dependent Factors
Limiting factor that depends on population size
Usually strong when pop. is large and dense

16. Density-Dependent Factors
Include:
Competition
Predation
Predator-prey relationship: regulates population, best-known mechanism of pop. control
Parasitism
Disease

17. Predator-prey relationship

18. Density-Independent Factors
Affect all pops. the same, regardless of pop. size
Usually results in crash in pop. size, followed by building back up

19. Density-Independent Factors
Include:
Unusual weather
Natural disasters
Seasonal cycles
Certain human activities

20. Exit Slip
Give at least 2 factors that can be classified as density dependent and 2 density independent factors. Explain how density dependent factors affect the carrying capacity of an environment.

21. Section 5.3
Human Population Growth

22. Objectives
Describe how the size of human population has changed over time.
Explain why population growth rates differ from country to country.

23. Human Population Growth
The human population is still showing exponential growth

24. Population as of 9/28/10 at 11:04am
Population as of 10/26/09
U.S. 307,790, World 6,793,050,389
Population as of 9/28/10 at 11:04am
U.S. 310,359, World 6,871,700,813

25. Patterns of Population Growth
Demography: scientific study of human populations
Birth/death rates and age structure of pop. help predict why countries grow at different rates

26. Demographic transition
A dramatic change in birth/death rates
Change from high birth rate and high death rate to low birth rate and low death rate
So far, countries that have completed this transition include U.S., Japan, much of Europe

27. Age Structure
Shows how many people of different ages make up population
Constructing an age pyramid can give information about the growth rate.

28. Age-structure pyramids for the human population of Kenya (growing at 2
Age-structure pyramids for the human population of Kenya (growing at 2.1% per year), the United States (growing at 0.6% per year), and Italy (zero growth) for 1995

29. What’s going to happen to human population growth????
Estimates for Earth’s carrying capacity range from 2 billion to 40 billion.